The Fabrication Of Functional Three Dimensional Graphenewith The Assistant Of Supercritical CO₂ For High-performance Supercapacitor Applications

Graphene, a novel one-atom-thick two-dimensional nanomaterial, has attracted much attention, owing to its outstanding chemical and physical properties. In order to expand the application of graphene-based materials in environment, energy, biological and sensing fields, it is necessary to assemble 2D graphene sheets into 3D architectures. It may furnish graphene materials with higher specific surface areas, stronger mechanically strengths and faster mass and electron transport kinetics because of the combination of 3D porous structure and the outstanding intrinsic properties of graphene. Building three-dimensional graphene-based hybrid nanostructures with anticipated function has become one of the most active research fields. Considering the single-phased nanomaterials always have their intrinsic defects, scientists are inclined to combine unique properties of individual nanostructures and explore their synergistic effect.Considering its low viscosity, high diffusivity, zero surface tension, and plasticization to polymer, SC CO2 has been applied in the fabrication of nanomaterials. In view of the soft matter theory and the great tunabililty of SC CO2, it is anticipated that nanocomposites of tailored structure and controlled assembly of nanoparticles can be achieved with the help of SC CO2. Therefore, the main content of my research subject includes:(1) The architectures of 3D graphene-pyrrole/carbon nanotube/polyaniline(GPCP) nanohybrids can be successfully prepared by dipping the G-Py aerogel into the CNT/PANI nanocomposites solution. The incorporation of CNT/PANI into the porous structures of graphene-based foam could prevent aggregation/restacking of graphene sheets to miantian the foam architectures. Also, the well deposition of PANI nanorods on CNT effectively increases the electrochemical utilization of PANI, and reduces the ion diffusion path in the process of charge-discharge, which result in outstanding electrochemical properties.(2) Graphene-pyrrole(G-Py) aerogels was prepared by a green hydrothermal route,while CNT/PANI composite dispersion was obtained via in-situ polymerization method. Then a series of nanohybrids were successfully prepared with the assistance of supercritical CO2(SC CO2), which could be used as efficient electrode materials for supercapacitors. The obtained nanohybrids were characterized by fourier transform infrared spectroscopy(FT-IR), X-ray diffraction(XRD), Raman, and we further evaluated their electrochemical performance. It was fascinating to observe that the nanohybrid prepared through one step method with the assistance of SC CO2 had superior performance.(3) We have demonstrated that 3D graphene-pyrrole/carbon nanotube/polyaniline(GPCP nanohybrids) can be successfully prepared with the assistant of SC CO2. Electrochemical studies illustrate that the obtained composites show a high specific capacitance of 400 F g-1, which is 1.4 times that of the nanohybrids without the assistance of SC CO2. The experimental results are a proof of concept that SC CO2 is an efficient method to help achieve hierarchical multi-component nanohybrids and as well as it may guide the way for designing new functional materials that can be used as electrode materials for lightweight and flexible energy storage device in the near future.